Korea Electrotechnology Research Institute

Gallium-based liquid metals (LMs) are promising materials for stretchable electronics due to their metallic conductivity and deformability. However, the fabrication of large-area stretchable integrated electronics using LMs on various polymers remains challenging due to their high surface tension, fluidity, and poor wettability. Current techniques, such as selective wetting and lift-off processes, face limitations related to substrate compatibility and Ga/metal alloying, hindering their applicability in integrated electronic systems. To address these challenges, we developed a high-resolution top-down etching-based photolithography combined with a universal cryogenic transfer method for transferring patterned LM particles (LMPs) in various polymer substrates. The cryogenic environment modifies the interfacial bonding between the LMPs and substrates, resulting in a universal transfer. The resulting liquid metal particle network embedded polymer (LNEP) exhibits high electrical conductivity (~1.71 × 10⁶ S/m), stability, and strain-insensitive performance across various polymers. This process is scalable to large-area fabrication, overcoming the limitations of existing LM patterning techniques. Leveraging this approach, we demonstrated the use of LNEP ranging from skin-conformal wearable sensors to hybrid stretchable circuits and implantable devices, demonstrating the universality of the method. This technique establishes a scalable pathway for stretchable electronics in advanced applications.

ABSTRACT All‐solid‐state batteries (ASSBs) are among the most promising candidates for next‐generation energy storage due to their high energy density and intrinsic safety. However, the practical use of lithium metal anodes in ASSBs remains limited by interfacial instability and dendritic Li growth, particularly under moderate stack pressures. Here, we report a nano‐sized tin (nSn) interlayer that forms a highly reversible Li–Sn alloy interface via spontaneous in situ lithiation, offering a robust, lithiophilic, and electronically conductive interface between the Li metal and sulfide‐based solid electrolyte. The resulting Li x Sn layer promotes uniform Li‐ion transport, suppresses dendrite formation, and enhances interfacial charge transfer. Symmetric cell measurements demonstrate markedly improved critical current densities and stable cycling, while full‐cell tests reveal high Coulombic efficiency, improved rate performance, and excellent capacity retention. The nSn interlayer was further scaled into a sheet‐type architecture using a warm isostatic press (WIP) process for integration into pouch‐type cells. The pouch cell exhibited high areal capacity, retaining 81% after 500 cycles, and delivered energy densities of 351 Wh kg −1 and 918 Wh L −1 under a low external pressure of 2 MPa. This work introduces a simple and scalable alloying‐based interfacial engineering strategy that enables high‐performance, fast‐charging ASSBs with practical viability.

Abstract Artificial neural networks underpin modern artificial intelligence but face challenges of scalability, energy consumption, and hardware efficiency as model sizes grow. Photonic approaches offer an attractive alternative by exploiting the parallelism and low thermal footprint of light, yet many implementations still require complex device fabrication or engineered nonlinearities. Extreme learning machines (ELMs) simplify this paradigm by fixing the input‐to‐hidden mapping and training only a linear output layer, making them highly compatible with physical realizations. Here, a photonic ELM (PELM) framework is introduced based on ultrafast transient absorption (TA) spectroscopy, a widely adopted pump–probe technique operating intrinsically on the femtosecond–picosecond timescale. In this system, inputs are encoded through multiple probe‐polarization channels, each parameterized by pump–probe delay, and the resulting TA spectral responses provide high‐dimensional nonlinear features without pixelated modulators or nanofabrication. Using a quasi‐1D ZrSe 3 nanoribbon, task versatility is demonstrated across nonlinear regression, spiral classification, and image recognition. The approach achieves near‐perfect accuracy on the Iris dataset and robust performance on MNIST digits, underscoring the potential of TA‐based encoding for physical computation. These results establish ultrafast TA spectroscopy as an experimentally accessible platform and lay the groundwork for future ultrafast, energy‐efficient photonic learning systems.

Solid-state electrolytes (SSEs) have received significant attention as a means to improve the energy density and safety of lithium (Li) batteries. However, their electrochemical performance is critically dependent on the quality of interfacial contact between constituent particles, particularly within the cathode composite. To ensure intimate contact between the SSE and the cathode active material, the use of small SSE particles in 1-3 μm dimensions is essential. Here, we report a one-pot synthesis of argyrodite-type Li6PS5Cl (LPSCl) particles with an average size of ∼2 μm, achieved without any post-processing steps. The key strategy was the use of a solvent with strong Li+ solvation capability, specifically 1,2-dimethoxyethane (DME), based on the reaction of Li+ with naphthalene-derived radical anions. The Li+ solvation in DME prevents the formation of aggregative ion pairs between Li+ and anionic intermediates, such as polysulfides, polythiophosphates, and chlorides. This stabilization of free Li+ governed nucleation and evolution of LPSCl particles via a precipitation-dissolution-reprecipitation process. The use of DME enabled the synthesis of smaller and also higher purity particles compared to weaker solvating solvents such as tetrahydrofuran (THF) and 2-methyl-THF, leading to superior ionic conductivity (3.3 mS cm-1 at 30 °C) and a high critical current density (1.75 mA cm-2). When applied in full cells using LiNbO3-coated NCM811 cathodes, the cells demonstrated remarkable cycling stability, retaining 99.7% of their capacity after 1000 cycles at 1.0 C and 55 °C, providing excellent contact between the small-size LPSCl and NCM811.

All-solid-state batteries (ASSBs) have garnered increasing attention owing to their enhanced safety and the ability to deliver high energy density. Among various anode candidates for ASSBs, silicon oxide (SiO x ) is notable due to its mitigated volume change during cycling and improved durability compared to pure silicon. Nonetheless, the electrochemical performance is often hindered by insufficient contact at the interface between active components and sulfide-type solid electrolytes (SEs), largely resulting from void formation during conventional mixing processes. To overcome this limitation, we employed a mechano-fusion (MF) technique to prepare SiO x –SE composite structures. In this approach, ductile Li 6 PS 5 Cl was conformally coated onto the surface of SiO x particles via high-shear mechanical compression in the absence of solvents and binders. This method enhances interfacial adhesion, minimizes void generation, and facilitates continuous ion transport within the electrode. Compared with conventionally ball-milled electrodes, those fabricated using MF exhibited superior capacity retention (27.56 % vs. 58.61 %) and better performance under high-rate conditions, indicating enhanced cycling durability. These findings demonstrate that the MF process offers a robust interfacial engineering strategy for ASSBs and suggests its potential for scalable application in high-performance solid-state anodes. • Mechano-fusion was applied to enhance interface contact in SiO x -based ASSBs. • Dense SE coating on SiO x improved ionic conductivity and reduced polarization. • Coexistence of SE and carbon layers balanced ionic and electronic conduction. • MF process improved long-term cycling and high-rate performance in ASSBs.

Abstract Oxide-based solid electrolytes promise safe, high energy density all-solid-state batteries (ASSBs), but require high sintering temperature, which impairs cathode-electrolyte compatibility and manufacturability. Incorporating Ag nanoparticles enables low-temperature densification of a γ-Li3PO4-type LISICON (Li3.5Ge0.4Si0.1V0.4O4) via a ‘silver-zipping’ mechanism that transiently hosts Li, reduces local coulomb repulsion between solid electrolyte particles, and accelerates neck growth. The resulting microstructure yields higher ionic conductivity without a measurable rise in electronic conductivity, serves as both separator and catholyte, and co-processes with layered oxides at ≤ 750°C without parasitic phases. The strategy provides a practical route to low-temperature processing of oxide-based ASSBs with improved interfacial compatibility and manufacturability.

High-Mass Loading SiOx Anodes In their Research Article (10.1002/adfm.202517642), Hyung-Seok Kim, Seong Ku Kim, Sunho Jeong, and co-workers design digitally programmable 3D printing and mid-IR laser annealing techniques for resolving intrinsic transport limitations of thick SiOx anodes. The 3D-printed and laser-annealed, hierarchically porous SiOx anode achieves an areal capacity of 9.5 mAh cm−2 (specific capacity: 1,309 mAh g−1, mass loading: 6.6 mg cm−2) with a capacity retention of 87.7% after 100 cycles.

To establish a reliable thermoelectric module evaluation, a Standard Reference Thermoelectric Module (SRTEM) was developed based on stability. Open-circuit voltage (Voc) was selected as the key calibration parameter due to its consistent response to temperature differences (ΔT). The SRTEM consists of eight p–n thermoelectric couples composed of metallic thermoelectric materials—Ni90Cr10 (chromel), Cu55Ni45 (constantan), Fe64Ni36 (invar), and pure Fe—selected based on their thermoelectric properties, structural compatibility, and contact resistance. Among the tested combinations, the chromel–constantan pair exhibited the highest Voc of 55 mV at ΔT = 150 K. To increase Voc and expand the usable calibration range, leg-shape modification and substrate replacement were investigated. Module simulation revealed that replacing the rectangular-leg geometry with a double-hourglass (2H/G) structure could increase Voc by 20.2%. Furthermore, measurement of single-leg modules with substrates attached confirmed a 16.0% improvement in Voc for the 2H/G shape over the rectangular shape, consistent with the predicted enhancement due to increased thermal resistance. In addition, replacing the alumina substrate with a higher thermal conductivity material, such as AlN, increased ΔT across the legs and yielded a further 9.1% improvement in Voc. These results demonstrate the potential of the proposed SRTEM as a calibration standard for consistent thermoelectric module measurements.

This paper presents a multi-input single-output power combine-and-regulate (MISO-PCR) converter chip for a 5.8GHz WPT receiver (Rx). The MISO-PCR simultaneously collects, combines, and converts the multiple power from 30 GaAs rectennas into a single regulated output (28V). Fabricated in a 180nm BCD, the chip enables the Rx system—paired with a beamforming Tx—to deliver a 3.1 W power at a 50m distance.